Download Chapter 17 Immune Response

Chapter 17
Immune response
• Two types of resistance.
• Innate resistance and acquired resistance.
• Innate resistance – one is born with the
resistance.
• All humans are resistant to certain animal
diseases such as canine distemper.
• Distemper virus infects the nervous
system of dogs.
• Humans can’t get the disease because
humans do not have the receptor for the
virus.
• Acquired resistance (acquired immunity)
• Resistance is acquired during one’s
lifetime.
• Immunity is a specific defense response
• Interaction between an antigen and the
immune system.
• Antigen is a foreign substance.
• Bacteria, pollen, insect venom,
transplanted tissue.
Different classes of antibodies
• IgG – 80% of the antibodies in the serum.
• Cross placenta and give passive immunity
to the fetus.
• Protect against viruses, bacteria and
toxins that are circulating in the body
fluids.
• Activates the complement system.
• Enhances phagocytosis.
• IgM – 5 to 10%, pentamers
• First antibody to show up in response to
initial infection.
• Activates the complement system.
• Agglutinates antigens
• IgA – 10 to 15%
• Found in body secretions – mucus, saliva,
tears.
• Secretory IgA is a dimer.
• Prevent the attachment of bacteria and
viruses to the mucosal sufaces.
• IgD – 0.2% of the serum antibodies
• Found on the surface of the B
lymphocytes.
• Functions as an antigen receptors.
• IgE – 0.002% of the serum antibodies
• Involved in allergic reactions.
• Humoral immunity – B lymphocytes
• Antibodies
• Cell mediated immunity – T lymphocytes
Cell mediated immunity
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T cells have receptors for antigen.
Clonal selection is involved.
Memory cells are made
When T cells are stimulated by antigen,
they do not make antibodies.
• They make proteins known as cytokines.
• T cells do not respond to antigens floating
around in the body fluids.
• They respond to intracellular antigens.
• Antigen has to be processed and
presented to the T cells by an antigen
presenting cell – macrophage.
Different types of T lymphocytes
• Helper T cells – TH
• Cytotoxic T cells – TC
• Suppressor T cells - Ts
surface
Ruffled
larger
• T independent antigens are
polysaccharide antigens such as those
found in the capsules of bacteria.
• B cells can make antibodies on their own
against these antigens.
• They do not need any help from the T
cells.
• T dependent antigens – proteins such as
those found in the capsids of viruses. B
cells cannot make antibodies against
these on their own.
• They have to get help from helper T cells.
Suppressor T cells
• Prevent the anibodies from attacking one’s
own cells.
• Stop the immune response once the
antigen has been removed from the
system.
Natural killer cells
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Different class of lymphocytes.
They come in contact with tumor cells.
Produce toxins.
Destruction of the tumor cells
Antibody dependent cell mediated
cytotoxicity